There has been proposed a rotary head type digital tape recorder for recording/reproducing a digital audio signal (PCM signal) by a pair of rotary heads. In such a digital tape recorder, sub codes such as the program number, the time code, and the like are recorded. In addition, PCM-IDs for identifying the sampling frequency, the number of channels, and the number of digitization bits of the PCM signal, the presence or absence of preemphasis, the characteristic thereof, and the like are recorded together with the PCM signal.
In the proposed digital tape recorder, the PCM signal can be input and output in the form of serial data in order to be able to supply an analog audio signal as the recording input signal, to obtain an analog audio signal as the reproduction output signal, and to make it possible to easily digitally couple with other PCM apparatuses such as other digital tape recorders, digital mixers, and the like. In this case, it is necessary to transmit the sub data together with the PCM signal. Several formats have been proposed by EBU, Philips, and others as standards for the PCM signal transmitting systems. According to the format of EBU, the auxiliary bits of four bits and the user data of one bit for the sub code of the compact disc are assigned to one audio sample data. According to the format of Philips, the PCM signal and the other data are multiplexed when transmitted and received.
In the case of the proposed rotary head type digital tape recorder, there is a large amount of sub data of the sub codes and PCM-ID. Therefore, the sub data cannot be transmitted by any of these conventional PCM signal transmitting systems.